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Search Results: 1 - 10 of 25287 matches for " Junseong Lee "
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2,8,9-Tris(2-methylpropyl)-2,5,8,9-tetraaza-1λ5-phosphatricyclo[,5]undecan-5-ium chloride dihydrate
Junseong Lee,Youngjo Kim
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812045618
Abstract: The asymmetric unit of the title hydrated salt, C18H40N4P+·Cl ·2H2O, consists of two ionic molecules and four water molecules. The molecular geometry around the pentacoordinate P atom is trigonal–bipyramidal, with a H atom and an apical N atom in axial positions and three N atoms with isobutyl substituents in equatorial positions. The Cl ions and water molecules are connected via O—H...Cl hydrogen bonds, forming chains along [100]. The ethylene bridging groups are disordered with refined site-occupancy ratios of 0.578 (9):0.422 (9).
Junseong Lee,Youngjo Kim
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811027814
Abstract: The dinuclear title complex, [Ti2(C10H15)2(C7H2F5O)4O], features two TiIV atoms bridged by an O atom. Each Ti atom is bonded to a η5-pentamethylcyclopentadienyl ring, two (pentafluorophenyl)methanolate anions and to the bridging O atom. The environment around each Ti atom can be considered as a distorted tetrahedron.
Junseong Lee,Youngjo Kim
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811029357
Abstract: The dinuclear title complex, [Ti2(C10H15)2(C6F5O)4O], features two TiIV atoms bridged by an O atom, which lies on an inversion centre. The TiIV atom is bonded to a η5-pentamethylcyclopentadienyl ring, two pentafluorophenolate anions and to the bridging O atom. The environment around the TiIV atom can be considered as a distorted tetrahedron. The cyclopentadienyl ring is disordered over two sets of sites [site occupancy = 0.824 (8) for the major component].
Mitochondrial Network Determines Intracellular ROS Dynamics and Sensitivity to Oxidative Stress through Switching Inter-Mitochondrial Messengers
Junseong Park,Jungsul Lee,Chulhee Choi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0023211
Abstract: Oxidative stresses caused by reactive oxygen species (ROS) can induce rapid depolarization of inner mitochondrial membrane potential and subsequent impairment of oxidative phosphorylation. Damaged mitochondria produce more ROS, especially the superoxide anion (O2?) and hydrogen peroxide (H2O2), which potentiate mitochondria-driven ROS propagation, so-called ROS-induced ROS release (RIRR), via activation of an inter-mitochondria signaling network. Therefore, loss of function in only a fraction of mitochondria might eventually affect cell viability through this positive feedback loop. Since ROS are very short-lived molecules in the biological milieu, mitochondrial network dynamics, such as density, number, and spatial distribution, can affect mitochondria-driven ROS propagation. To address this issue, we developed a mathematical model using an agent-based modeling approach, and tested the effect of mitochondrial network dynamics on RIRR for mitochondria under various conditions. Simulation results show that the intracellular ROS signaling pattern, such as ROS propagation speed and oxidative stress vulnerability, are critically affected by mitochondrial network dynamics. Mitochondrial network dynamics of mitochondrial distribution, density, activity, and size can mediate inter-mitochondrial signaling under certain conditions and determine the identity of the ROS signaling pattern. We further elucidated the potential mechanism of these actions, i.e., conversion of major messenger molecules involved in ROS signaling. If the average distance between neighboring mitochondria is large or mitochondrial distribution becomes randomized, messenger molecule of the ROS signaling network can be switched from O2? to H2O2. In this case, mitochondria-driven ROS propagation is efficiently blocked by introduction of excess cytosolic glutathione peroxidase 1, while introduction of cytosolic superoxide dismutase has no effect. Together, these results suggest that mitochondrial network dynamics is a major determinant for cellular responses to RIRR through changing the key messenger molecules.
Sungwoo Yoon,Junseong Lee,Youngjo Kim
Acta Crystallographica Section E , 2013, DOI: 10.1107/s1600536813002006
Abstract: The title compound, C24H26O, was prepared by the reaction between 2-tert-butyl-4-methylphenol and diphenylmethanol in the presence of sulfuric acid. Three benzene rings are attached directly to the central C—H group in a twisted propeller conformation with the local pseudo-C3 rotational axis coinciding with the C—H bond. There are three short C—H...O contacts in the molecule.
Min Jeong Go,Ka Hyun Park,Hwi Hyun Lee,Junseong Lee
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812032783
Abstract: In the title compound, C14H13NOS, the dihedral angle formed by the mean planes through the indane ring system and the thiophene ring is 85.04 (11)°. The imine bond is located in the thiophene plane [the S—C—C—N torsion angle is 0.00 (3)°] and an intramolecular O—H...N hydrogen bond is observed.
Mutant Ubiquitin Attenuates Interleukin-1β- and Tumor Necrosis Factor-α-Induced Pro-Inflammatory Signaling in Human Astrocytic Cells
Kyungsun Choi, Junseong Park, Jungsul Lee, Eun Chun Han, Chulhee Choi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067891
Abstract: A frameshift mutation of ubiquitin called ubiquitin+1 (UBB+1) was found in the aging and Alzheimer’s disease brains and thought to be associated with neuronal dysfuction and degeneration. Even though ubiquitylation has been known to regulate vital cellular functions mainly through proteasome-dependent degradation of polyubiquitinated substrates, proteolysis-independent roles of ubiquitylation have emerged as key mechanisms in various signaling cascades. In this study, we have investigated the effect of UBB+1 on proinflammatory signaling such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in human astrocytes. Treatment with TNF-α and IL-1β induced expression of CCL2 and CXCL8 by human astrocytic cells; while ectopic expression of UBB+1 significantly abrogated the proinflammatory cytokine-induced expression of chemokines. Ectopic expression of UBB+1 suppressed TNF-α- and IL-1β-induced activation of NF-κB and JNK signaling pathway. Furthermore, we have demonstrated that polyubiquitylation of TRAFs and subsequent phosphorylation of TAK1 were significantly inhibited by stable expression of UBB+1. Collectively, these results suggest that UBB+1 may affect proinflammatory signaling in the central nervous system via inhibitory mechanisms of ubiquitin-dependent signaling in human astrocytes.
Phenotypic Modulation of Primary Vascular Smooth Muscle Cells by Short-Term Culture on Micropatterned Substrate
Soyoung Chang, Seungjeong Song, Jungsul Lee, Jonghee Yoon, Junseong Park, Sungyoung Choi, Je-Kyun Park, Kyungsun Choi, Chulhee Choi
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088089
Abstract: Loss of contractility and acquisition of an epithelial phenotype of vascular smooth muscle cells (VSMCs) are key events in proliferative vascular pathologies such as atherosclerosis and post-angioplastic restenosis. There is no proper cell culture system allowing differentiation of VSMCs so that it is difficult to delineate the molecular mechanism responsible for proliferative vasculopathy. We investigated whether a micropatterned substrate could restore the contractile phenotype of VSMCs in vitro. To induce and maintain the differentiated VSMC phenotype in vitro, we introduced a micropatterned groove substrate to modulate the morphology and function of VSMCs. Later than 7th passage of VSMCs showed typical synthetic phenotype characterized by epithelial morphology, increased proliferation rates and corresponding gene expression profiles; while short-term culture of these cells on a micropatterned groove induced a change to an intermediate phenotype characterized by low proliferation rates, increased migration, a spindle-like morphology associated with cytoskeletal rearrangement and expression of muscle-specific genes. Microarray analysis showed preferential expression of contractile and smooth muscle cell-specific genes in cells cultured on the micropatterned groove. Culture on a patterned groove may provide a valuable model for the study the role of VSMCs in normal vascular physiology and a variety of proliferative vascular diseases.
Z_3 Strings and their Interactions
Junseong Heo,Tanmay Vachaspati
Physics , 1998, DOI: 10.1103/PhysRevD.58.065011
Abstract: We construct Z_3 vortex solutions in a model in which SU(3) is spontaneously broken to Z_3. The model is truncated to one in which there are only two dimensionless free parameters and the interaction of vortices within this restricted set of models is studied numerically. We find that there is a curve in the two dimensional space of parameters for which the energy of two asymptotically separated vortices equals the energy of the vortices at vanishing separation. This suggests that the inter-vortex potential for Z_3 strings might be flat for these couplings, much like the case of U(1) strings in the Bogomolnyi limit. However, we argue that the intervortex potential is attractive at short distances and repulsive at large separations leading to the possibility of unstable bound states of Z_3 vortices.
Preparation of Thiophene-Fused and Tetrahydroquinoline-Linked Cyclopentadienyl Titanium Complexes for Ethylene/α-Olefin Copolymerization
Sung Hun Kim,Ji Hae Park,Bo Geun Song,Seung-Woong Yoon,Min Jeong Go,Junseong Lee,Bun Yeoul Lee
Catalysts , 2013, DOI: 10.3390/catal3010104
Abstract: A synthetic scheme was developed for the large-scale preparation of a dimethylthiophene-fused and tetrahydroquinaldine-linked dimethylcyclopentadienyl titanium complex ( 2), which is a high-performance homogeneous Ziegler catalyst. 2,3,4,5-Tetramethyl-4,5-dihydrocyclopenta[ b]thiophen-6-one was prepared without chromatography purification on the 40-g scale in a laboratory setting, from which the ligand precursor for 2 was obtained in 65% yield on a 50-g scale in a one-pot without the need for chromatography purification. Metallation was achieved in a high yield (78%) through reaction of the dilithiated compound with TiCl 4. Many derivatives were prepared by employing the same synthetic scheme as applied for 2. Among them, the titanium complex prepared from 2-methyl-4,5-dimethyl-6-(2- n-butyl-2,3,4,5-tetrahydroquinolin-8-yl)-4 H-cyclopenta[ b]thiophene exhibited an exceptionally high activity. Under commercially relevant high-temperature polymerization conditions (160 °C), this compound showed a higher activity than 2 (126 × 10 6 g/molTi?h versus 72 × 10 6 g/molTi?h), albeit with the formation of a polymer of slightly lower molecular weight ( M w, 159,000 versus 218,000) and with a slightly lower 1-octene content (9.3 mol% versus 12 mol%).
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